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Stardate 4/15/14: Arcturus Shines Bright, But Not Forever

by Damond Benningfield
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FROM THE UNIVERSITY OF TEXAS McDONALD OBSERVATORY, AS HEARD ON KCBS RADIO WEEKDAYS @ 9:52 A.M., 7:35 P.M. & 2:52 A.M.

StarDate 4/15/2014: The star patterns that form pretty pictures in the night sky are all temporary. Over time, their shapes will change, erasing the old pictures and creating new ones. It’s not something that’s visible in a human lifetime — or, with a few exceptions, in a hundred lifetimes.

One of those exceptions is Arcturus, one of the brightest stars in the night sky. The yellow-orange star is in the east as the sky gets good and dark, well to the upper left of the Moon. Don’t confuse it with the brighter orange light that’s above the Moon — the planet Mars.

One reason Arcturus shines so brightly is that it’s a close neighbor — just 37 light-years away. In fact, it’s about as close right now as it ever will be.

Arcturus is racing across the sky at about 270,000 miles per hour relative to our own solar system — roughly the distance from Earth to the Moon. That’s faster than any of the other especially bright stars in the night sky. As a result of that motion, Arcturus will fade from view in a hurry — astronomically speaking. A million years from now it’ll be lost from view.

In the meantime, its motion will drastically alter the pictures of a couple of constellations. Today, Arcturus is the leading light of Bootes, the herdsman. But 50,000 years from now it’ll have moved one constellation over, and will be shining near the bright star that lines up between the Moon and Mars tonight — Spica, the leading light of Virgo.

Copyright ©2014 The University of Texas McDonald Observatory

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